Desktop and Laptop computers
It is best to use a modern and relatively new computer. Generally speaking, if your computer is more than 6 years old, you may experience issues with performance.
iOS and Android Smart Phones
Video streaming is an intensive process. If the phone of the person you are calling is 4 or 5 + years old, it may experience issues with performance. Modern phones are much faster, have better cameras, and generally have a better probability of connecting and displaying smooth video.
Headset with Microphone
As with any form of communication, it is best to be heard and reduce noise where possible. Use a headset with a microphone to reduce background noise and send a quality audio signal to the person you are speaking with. Test your headset before using and make sure audio levels are optimized for the highest quality.